Dehydration: The Negative Effects

Feb 12, 2020

We lose water on a daily basis. We exhale water when we breathe, we lose water through our skin as sweat and we excrete water in our urine. Without regularly replacing this fluid we become dehydrated. We can’t train our bodies to adapt to dehydration, unfortunately. It’s not something you can become good at. Even mild dehydration can have noticeable negative effects. Let’s take a look…

1. Fatigue

Perhaps the most noticeable effect of dehydration is a general feeling of fatigue. Being dehydrated is often the cause of headaches or headache-type symptoms such as reduced focus, dizziness, light-headedness, feeling tired and low mood. If you are feeling these effects, try drinking more water before jumping straight to taking painkillers.

2. Mental function

As dehydration increases, mental performance decreases. There is a noticeable impairment in short-term and working memory and our visual-motor function. Dehydration also impacts concentration and the ability to make decisions.

Dehydration of as little as 2% of body weight impairs performance in tasks that require attention, memory skills and psychomotor skills (such as driving a car, riding a bike, throwing a ball). Not ideal as an athlete!

3. Physical Performance

We know that dehydration of as little as 2% of your body weight also affects your ability to physically perform at your best.

How much is 2%? As an example, for a 60kg person, that’s only 1.2kg of body weight loss over a session.

Dehydration increases our body temperature, heart rate and perception of effort (how hard you feel you’re working). It also makes fatigue set in earlier, especially in the heat. Couple this with a decrease in mental function and we reduce our ability to perform skills like riding a bike or catching a ball. Our decision making is also reduced so we increase our risk of injury and falling off the bike!

During exercise, the body cools itself by sweating – which results in a loss of body fluid. We know this fluid loss increases as both temperature, humidity and exercise intensity increase but there are a range of other factors that affect your sweat rate such as body size, genetics and fitness levels.

Because sweat rates vary so much for individuals and there’s not one set value for everyone, it’s important to know your own unique sweat rate. This will help you understand how much fluid you should be drinking throughout the exercise and afterwards to prevent dehydration and rehydrate effectively.

In most cases, allowing your thirst to guide you is a terrible way to stay well hydrated. If you feel thirsty, chances are you’re already a little dehydrated!

Instead, it’s important to know what sort of sweater you are and develop a personalised hydration plan. If this is something you’re interested in, book in for a Sweat Testing Sessionwith a qualified Sports Dietitian today! DO NOT do a self-test kit at home as these are highly unreliable and inaccurate.